"My brother is doing a lot better," Patrick tweeted yesterday from his account, which now lists him as, ahem, Patrick Shriver. "Wearing this shirt for him."

This shirt, as it happens, features a Shepard Fairey-style image of his little bro. Clearly made in honor of his last birthday (it bears the day he turned 13), the shirt reads "Christopher is a teenager 09-27-10."

The health update comes a week after the teen was hospitalized after sustaining serious injuries while boogie boarding in Malibu. His mother, who was with him at the time, phoned 911 after the incident, and Christopher was admitted into the intensive care unit.

"It's like a boogie board accident, I think, he can't move off the beach, maybe like a broken rib or something like that...It's my son," Shriver calmly told the dispatcher in the call obtained by E! News. "He's awake and breathing, he just can't move, he's having trouble breathing."

In addition to his mom, all members of his family—including brother Patrick, sisters Christina and Katherine and, yes, father Arnold —have visited him in the hospital.

As Patrick's Twitter message indicates, Christopher's condition has been upgraded and he's expected to make a full recovery. Get well soon!